Classifications

• • C—CHEMISTRY; METALLURGY
  • C08—ORGANIC MACROMOLECULAR COMPOUNDS; THEIR PREPARATION OR CHEMICAL WORKING-UP; COMPOSITIONS BASED THEREON
  • C08F—MACROMOLECULAR COMPOUNDS OBTAINED BY REACTIONS ONLY INVOLVING CARBON-TO-CARBON UNSATURATED BONDS
  • C08F10/00—Homopolymers and copolymers of unsaturated aliphatic hydrocarbons having only one carbon-to-carbon double bond
  • C08F10/02—Ethene

Definitions

• MFI melt flow index
• the present invention relates to a process for the preparation of these ethylene homopolymers and copolymers.
• the initiators used in the (n-1) th stage have a half-life temperature of 80 to 160 ° C.
• These known ethylene homopolymers and copolymers are, however, comparatively low molecular weight and easily flowing with melt indices of 2.5 to 3.5. If you want the process known from EP-A-0 394 794 for the production of higher molecular weight, less easily flowing homopolymers and copolymers, explosive ethylene decomposition occurs regularly in the reactors, which prevents the polymerization from being carried out safely and reliably.
• EP-A-0 394 794 also shows that the nth polymerization stage can also be initiated by an initiator with a half-temperature of up to 250 ° C.
• an initiator with a half-temperature of up to 250 ° C. Examples include tert-butyl perbenzoate and methyl isobutyl ketone hydroperoxide.
• the initiators with a low half-temperature are replaced by methyl isobutyl ketone hydroperoxide and the polymerization is carried out so that the maximum reaction temperatures T max are below 270 ° C., then point the resulting ethylene homopolymers only have densities of less than 921.5 kg / m3.
• the object of the invention was to remedy the disadvantages of the process known from EP-A-0 394 794 and to achieve ethylene homopolymers and copolymers with densities of 925 to 940 kg / m 3 and a melt flow index (melt flow index , MFI) at 190 ° C and a tracking force of 2.16 kp of ⁇ 1 g / 10 min and good optical properties with high turnover.
• melt flow index MFI
• these new ethylene homopolymers and copolymers are said to provide mechanically strong and highly stretchable films with excellent optical properties.
• the process used to prepare the polymers according to the invention can be used both for the homopolymerization and for the copolymerization of ethylene with other monomers, provided that these monomers undergo radical copolymerization with ethylene under high pressure.
• suitable copolymerizable monomers are ⁇ , ⁇ -ethylenically unsaturated C3 to C8 carboxylic acids, in particular maleic acid, fumaric acid, itaconic acid, acrylic acid, methacrylic acid and crotonic acid, ⁇ , ⁇ -ethylenically unsaturated C bis to C15 carboxylic acid esters or anhydrides, especially methyl methacrylate, Ethyl acrylate, n-butyl acrylate, methacrylic anhydride, maleic anhydride and itaconic anhydride.
• the comonomer content in the invention Copolymers should not exceed 40, in particular 20% by weight.
• the polymerization is carried out at pressures of 500 to 5000 bar, pressures between 1500 and 3500 bar being advantageous.
• the reaction temperatures T are above 40 ° C. It is advantageous here if the reaction temperatures do not exceed T 320, in particular 300 ° C.
• the polymerization is started in its first stage by adding free-radical initiators.
• suitable initiators are organic peroxides such as peroxyesters, peroxyketones, peroxyketals and peroxycarbonates; Azodicarboxylic acid esters, azodicarboxylic acid dinitriles and free-radically decomposing hydrocarbons, which are also referred to as C-C starters.
• Examples of highly suitable initiators are di-2-ethylhexyl peroxydicarbonate, dicyclohexyl peroxydicarbonate, diacetylperoxydicarbonate, cumyl perneodecanoate, tertiary amyl perpivalate, tertiary butyl perneodecanoate, tertiary butyl permaleinate, tertiary butyl perylate , tert.-butyl perisononanoate, diisopropylbenzene hydroperoxide, cumene hydroperoxide, tert.-butyl perbenzoate, methyl isobutyl ketone hydroperoxide, 2,2-bis (tert.-butylperoxy) butane, azobisisobutyronitrile and 1,2-diphenyl-1,2-dimethyl-ethane and 1,1,2,2-tetramethylethane derivatives.
• the initiators can be used individually or as a mixture in concentrations of 0.5 to 100 and in particular 0.5 to 50 ppm / h, based on the amount of monomer. It is advantageous to use the initiators in the dissolved state.
• suitable solvents are aliphatic hydrocarbons, in particular octane and isodecane.
• initiators for the first stage of the polymerization which have a half-life temperature of 80 to 160 ° C.
• the half-value temperature is the temperature at which half of the initiator dissolved in benzene disintegrates within one minute.
• tert-butyl perpivalate and tert-butyl perisononanoate prove to be particularly advantageous and are therefore used with very particular preference.
• initiators used have a half-temperature of 90 to 260 ° C.
• suitable initiators with these half-life temperatures are diisopropylbenzene hydroperoxide, cumene hydroperoxide, tert-butyl perbenzoate, methyl isobutyl ketone hydroperoxide, 2,2-bis (tert-butyl peroxy) butane and 2,3-dimethyl-2,3-diphenylbutane, of which methyl isobutyl ketone hydroperoxide is particularly advantageous and is therefore used with very particular preference.
• molar mass can be controlled as usual by adding regulators.
• suitable regulators are aliphatic hydrocarbons, ketones and aldehydes, of which propionaldehyde is particularly advantageous and is therefore used with very particular preference.
• the process for the preparation of the polymers according to the invention is carried out with the practical exclusion of oxygen in at least three successive stages, the polymerization having to be restarted in each stage by adding the appropriate initiators.
• Tubular reactors which are provided with a series of inlet points for the initiator and, if appropriate, for the supply of further amounts of monomer, are suitable for the implementation.
• the tubular reactor has a length to diameter ratio of at least 1000, preferably more than 2000, with a length of 50 to 1000 m.
• the tubular reactor is advantageously arranged in a tortuous shape.
• the heat of reaction released during the polymerization is generally removed from the outside by cooling the reactor wall with water.
• a reactor with backmixing in particular a stirred autoclave, can also be connected upstream of the tubular reactor.
• the process is carried out without a heat exchanger.
• the used in the process Reactors generally contain a number of temperature measuring devices inside the reactor so that the temperature profile can be observed during the polymerization.
• T max is at or above 270 ° C. at least in the last, ie nth, stage of the polymerization.
• T max should generally not exceed 320, in particular 300 ° C.
• the reaction mixture of ethylene and a regulator and, if appropriate, at least one comonomer is first compressed to a pressure of more than 500, in particular 1500, bar, heated to over 100 ° C. and then together with a Part of the initiator fed into a tubular reactor, where the polymerization starts quickly after the initiator has decomposed.
• the reactor cooling should be set so that a T max of 320 ° C inside the tube is not exceeded in the first to the penultimate, ie (n-1) th stage.
• a temperature profile that depends on the polymerization conversion is established after a short time.
• the reaction mixture can either be spatially separated from the initiator at the same location or also spatially separated therefrom cold or preheated ethylene and / or cold or preheated comonomers can be added.
• the average residence time of the reaction mixture in the tubular reactor is between 30 and 300, in particular 30 and 120 seconds.
• the polymer according to the invention is separated by decompressing spent ethylene and, if appropriate, unused comonomer, after which the monomers are generally returned to the reactor.
• This process for the preparation of the polymers according to the invention can also be carried out in an analogous manner in a reactor with backmixing and a downstream tubular reactor.
• T max in the reactor with backmixing should not exceed 230 ° C.
• the polymerization mixture, together with the as yet unused monomers is introduced into the tube reactor through a high-pressure tube, which may also be connected to a heat exchanger, where the process is continued as described above.
• the average residence time of the mixture in the reactor with backmixing is 10 to 100, in particular 10 to 30 seconds, in the tubular reactor 10 to 200, in particular 10 to 100 seconds.
• the polymers according to the invention can be produced safely and exactly reproducibly, without causing an explosive decomposition of the ethylene in the reactors.
• the polymers according to the invention have densities of 925 to 940 kg / m3. Its melt flow index according to DIN 53 735 is less than 1, especially less than 0.5 g / 10 min. Films which are produced from the polymers according to the invention have good splicing capacity and outstanding optical properties. This is particularly evident in the relatively small amount of scattered light (according to DIN 53 490) and the increased gloss values (according to DIN 67 530). In the manner described above, it is possible to produce polymers according to the invention with densities of over 925 kg / m 3 and conversions of more than 25%.
• the polymers according to the invention are also obtained when the reaction mixture flows through the reactor at flow rates significantly lower than 0.307 m 2 / sec.
• the polymers according to the invention have excellent mechanical properties, which is evident from their high elongation at break, puncture resistance and the so-called "dart drop impact" values (DDI) measured according to ASTM D-1709-A.
• Examples 1 to 7 and comparative experiments A and B were carried out in a tubular reaction vessel with a length of 560 m and a ratio of length to diameter of 37,000.
• the polymerization initiators were dissolved in aliphatic hydrocarbons and fed directly to the feed points of the tubular reactor using high-pressure piston pumps.
• the position of the feed points determined the position of the reaction zones in the reaction vessel.
• the oxygen-free ethylene was compressed to the respective reaction pressure in several stages, a molar mass regulator was added and the inlet points of the tubular reactor were fed.
• Propionaldehyde or propane was used as the molecular weight regulator.
• the heat of reaction liberated during the polymerization was removed from the reaction mixture by means of a coolant circuit fed with steam.
• the resulting polymer was separated in a customary and known manner in the separators downstream of the reactor from unreacted ethylene and other low molecular weight compounds and discharged and packaged using an extruder and granulator. Unreacted ethylene was cleaned in several stages and returned to the suction side of the compressor.
• the drawability of the blown film was determined in a customary and known manner in the production of the film in question by extrusion, film blowing, peeling off the film and winding. The rate at which the blown film was withdrawn from the blower was gradually increased until the film broke.
• the resulting ethylene homopolymer according to the invention was freed of ethylene and low molecular weight impurities in a customary and known manner in high and low pressure separators, temporarily stored in bunkers and processed into blown films.
• Table 1 provides information on the conversion of the reaction, the physicochemical properties of the ethylene homopolymer according to the invention and the application properties of the blown film produced therefrom. Because of its excellent optical and mechanical properties, the ethylene homopolymer according to the invention was outstandingly suitable for the production of heavy goods packaging and small hollow bodies, and for the production of cable sheathing for low-voltage cables.
• Example 1 The resulting polymer was isolated, stored, examined and further processed as indicated in Example 1. The reaction conversion, the density, the melt flow index and the application properties of the blown films produced therefrom can also be found in the table.
• the reaction was not difficult and the feared explosive decomposition of ethylene did not occur.
• the ethylene homopolymer according to the invention was particularly suitable for the production of high-voltage cable sheathing, heavy goods packaging, small hollow articles for the medical sector and laminating films.
• the resulting ethylene homopolymer according to the invention was isolated, stored, examined and further processed as described in Examples 1 and 2.
• 1.6 t / h of ethylene was mixed with 0.85 l / h of propionaldehyde, compressed to 3000 bar, heated to 140 ° C. in a preheater and fed to the inlet of a tubular reactor.
• 3.5 ppm / h of tert-butyl perpivalate and 7 ppm / h of tert-butyl perisononanoate dissolved in isodecane were fed to the inlet point of the reactor. The polymerization was started in this way.
• the reaction mixture was cooled by adding 1.6 t / h of preheated ethylene, mixed with 0.85 l / h of propionaldehyde and compressed to 3000 bar, and 6 ppm / h of tert-butyl perpivalate and 12 ppm / h of tert-butyl perisononanoate dissolved in isodecane.
• the resulting ethylene homopolymer according to the invention was isolated, stored, investigated and further processed as described in Examples 1 to 3.
• the relevant data can also be found in the table. They show that the polymer according to the invention from Example 4 also has excellent performance properties and was excellently suited for all of the applications listed in the previous examples.
• 1.6 t / h of ethylene were mixed with 1.3 Nm3 / h of propane, compressed to 3000 bar, heated to 145 ° C. in a preheater and then fed to the entrance of a tubular reactor.
• 4 ppm / h of tert-butyl perpivalate and 8 ppm / h of tert-butyl perisononanoate dissolved in isodecane were also fed to the inlet point of the reactor. The polymerization was started in this way.
• the reaction mixture was preheated to 1.3 ° C. / h with propane by supplying 1.6 t / h to 125 ° C. mixed and cooled to 3000 bar compressed ethylene and mixed with 2 ppm / h tert-butyl perpivalate and 11 ppm / h tert-butyl perisononanoate dissolved in isodecane.
• the ethylene homopolymer according to the invention prepared in this way was isolated, temporarily stored, examined and further processed as described in the preceding examples.
• the relevant data can also be found in the table.
• 1.6 t / h of ethylene were mixed with 5000 ppm / h of n-butyl acrylate and 9.75 l / h of propionaldehyde, compressed to the reaction pressure of 300 bar, heated to 140 ° C. in a preheater and fed to the entrance of a tubular reactor.
• 3 ppm / h of tert-butyl perpivalate and 7 ppm / h of tert-butyl perisononanoate dissolved in isodecane were also fed to the inlet point of the reactor. The polymerization was started in this way.
• the reaction mixture was fed with 1.6 t / h with 5000 ppm / h n-butyl acrylate and 0.75 l / h added propionaldehyde, compressed to 3000 bar and preheated to 180 ° C. and mixed with 2 ppm / h tert-butyl perpivalate and 10 ppm / h tert-butyl perisononanoate in isodecane.
• the polymer according to the invention obtained in this way was isolated, stored, examined and further processed as described in the previous examples.
• the relevant data can be found in the table. They prove that this polymer according to the invention also had the same outstanding performance properties as the polymers according to the invention from example 1 to 5.
• Example 1 was repeated, except that the C-C starter 2,3-dimethyl-2,3-di-phenylbutane was used instead of methyl isobutyl ketone hydroperoxide.
• This initiator was added in an amount of 2 ppm / h in isodecane at the second and in an amount of 3.5 ppm / h at the third feed point.
• the resulting ethylene homopolymer according to the invention was isolated, stored, examined and further processed as in the previous examples. The relevant data can also be found in the table. They make it clear that the polymer of Example 8 according to the invention is very well suited for all of the applications mentioned in the previous examples. As far as the process is concerned, no ethylene decomposition occurs because of the use of the C-C starter.
• Comparative example B of EP-A-0 394 794 was repeated.
• 2.3 t / h of ethylene together with 2 l / h of propionaldehyde were compressed to 2800 bar in a high-pressure post-compressor, heated to 145 ° C. and fed into a tubular reactor.
• the polymerization was initiated by adding 4.8 ppm / h of tert-butyl perpivalate and 3.8 ppm / h of methyl isobutyl ketone hydroperoxide, which were added to the monomer at the inlet point of the tubular reactor.
• the polymerization was initiated again by twice adding 3.4 ppm / h of tert-butyl perpivalate and once by adding 2.2 ppm / h of methyl isobutyl ketone hydroperoxide, so that A total of four temperature maxima T max were formed, which did not exceed every 240 ° C. Otherwise, the resulting known ethylene homopolymer was isolated, stored, examined and further processed as described in Examples 1 to 8.
• the relevant data are in the table compared with the data of the ethylene homopolymers according to the invention. The data show that the known ethylene homopolymer had a lower density and a higher melt flow index than the polymers according to the invention. In addition, the film had significantly poorer application properties than the films of Examples 1 to 8.
• comparative example E of EP-A-0 394 794 was reworked.
• 1.4 t / h of ethylene together with 1.4 l / h of propionaldehyde were compressed to 2800 in a high-pressure post-compressor and fed into a stirred autoclave at a gas inlet temperature of 30 ° C.
• the polymerization was initiated by 10.4 ppm / h of tert-butyl perpivalate and the contents of the autoclave were mixed using a stirrer at a speed of 1300 rpm.
• the mean residence time was 25 seconds.
• the maximum temperature T max was 211 ° C.
• the reaction mixture was then introduced into the tube reactor via an insulated high-pressure tube. At the inlet point, 1.65 ppm / h of methyl isobutyl ketone hydroperoxide was added. After the temperature maximum T max had subsided and the polymerization had subsided, this was started again by 1.15 ppm / h of methyl isobutyl ketone hydroperoxide. This resulted in a total of two temperature maxima T max in the tubular reactor, both of which were below 270 ° C.
• the resulting known ethylene homopolymer was worked up, stored, examined and further processed as described in Comparative Example A.
• the data obtained in this way were compared with those of Examples 1 to 8 in the table.
• the comparison of the data shows how disadvantageous the known method is.
• an ethylene homopolymer is obtained which has a density of less than 921.5 kg / m3.

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• Chemical & Material Sciences (AREA)
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• Chemical Kinetics & Catalysis (AREA)
• Medicinal Chemistry (AREA)
• Polymers & Plastics (AREA)
• Organic Chemistry (AREA)
• Addition Polymer Or Copolymer, Post-Treatments, Or Chemical Modifications (AREA)
• Polymerisation Methods In General (AREA)
• Graft Or Block Polymers (AREA)
• Polymers With Sulfur, Phosphorus Or Metals In The Main Chain (AREA)

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Citations (4)

• 1991
  • 1991-09-26 DE DE4132012A patent/DE4132012A1/de not_active Withdrawn
• 1992
  • 1992-08-28 JP JP22981792A patent/JP3370353B2/ja not_active Expired - Fee Related
  • 1992-09-10 ES ES92115460T patent/ES2094261T3/es not_active Expired - Lifetime
  • 1992-09-10 EP EP92115460A patent/EP0534237B1/fr not_active Expired - Lifetime
  • 1992-09-10 DE DE59207584T patent/DE59207584D1/de not_active Expired - Lifetime
  • 1992-09-10 AT AT92115460T patent/ATE145652T1/de not_active IP Right Cessation
  • 1992-09-11 FI FI924074A patent/FI108354B/fi active
  • 1992-09-25 KR KR1019920017485A patent/KR100229703B1/ko not_active IP Right Cessation
• 1993
  • 1993-05-06 US US08/057,554 patent/US5306791A/en not_active Expired - Lifetime

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